1. Field of the Invention
The present invention relates to an engine starting and charging device that a starting motor for starting an engine and a charging generator driven by the engine to charge a battery are formed as one unit.
2. Prior Art
An engine starting and charging device comprising a starting motor and a charging generator as one unit has been suggested as a prior art, for example, one disclosed in laid-Open Japanese Patent No. Sho 61-54949.
FIG. 1 is a sectional view of a prior-art engine starting and charging device disclosed in Laid-Open Japanese Patent No. Sho 61-54959. In FIG. 1, a starting and charging device body 1 comprises revolving field poles 2a, 2b, a field coil 3, an armature core 4, an armature coil 5, and a crank angle detector 6 as major components.
The revolving field poles 2a, 2b are a pair of comb-shaped field poles produced of a ferromagnetic material, which are coupled as a unit through a ring 7 of non-magnetic material such that those magnetic pole sections are disposed alternately in the circumferential direction. The field pole 2a functions as a flywheel and also as a clutch carrier described later, is fitted on an engine crankshaft 8, and fixed on the end of the crankshaft 8 by a bolt 9. Numeral 10 is a cutout formed at the side portion of the field pole 2a, which, combined with the crank angle detector 6, is used to detect the crank angle; the same number of cutouts as the number of magnetic poles of the field pole 2a are provided at equal intervals around the circumference. The width of the cutout 10 in the circumferential direction makes an angle equal to about one half of 360 degrees divided by the number of the cutouts.
The field coil 3, which is for exciting the field poles 2a, 2b, is mounted on the field core 11. This field core is mounted and fixed to a rear plate 12 by bolts not illustrated, facing the field pole 2a across a slight gap a in the axial direction and the field pole 2b across a slight gap b in the diametrical direction.
The armature core 4 is formed by laminating silicon steel sheets, within the inner periphery of which are provided a large number of slots for setting the armature coil 5 therein, the armature coil 5 being of a three-phase distributed winding type as a common commutatorless motor. The armature core 4 is properly positioned and fixed in relation to a mounting frame 13, which is secured by bolts 14 to a rear plate 12 mounted on an engine body not illustrated. Numeral 15 is a spacer for axially securing the armature core 4 to the mounting frame 13, and numeral 16 is a spring ring.
The crank angle detector 6 serves as a signal source that operates an armature current switching circuit not illustrated, and uses an oscillation-type proximity switch. This proximity switch is so mounted on the rear plate 12 that its detecting element faces on the circumferential line where the cutouts 10 of the field pole 2a is provided, and its oscillating conditions vary with the change of inductance at the cutout and non-cutout sections of the field pole 2a, outputting a binary signal "1" and "0" corresponding to the crank angle (field pole position). When a three-phase armature coil 5 is employed, there will be installed three crank angle detectors 6.
Numeral 17 is a clutch which connects the engine crankshaft 8 to, or disconnects it from, a transmission drive shaft 18 for the interruption of power transmission, and uses a diaphragm spring clutch comprising a clutch disc 19, a pressure plate 20, a diaphragm spring (disc spring) 21, wire rings 22, 23, and a clutch cover 24. The clutch cover 24 is mounted by bolts 25 to the field pole 2a. The clutch 17 as such, as is well known, is of the constitution that when a clutch pedal (not illustrated) is not depressed, the tension of the diaphragm spring 21 is exerted to the clutch disc mounted on the transmission drive shaft 18 through the pressure plate 20 by lever ation, pressing this clutch disc 19 against the side of the field pole 2a and accordingly connecting the clutch.
When the clutch pedal is depressed, the sleeve, which is not illustrated, slides in the axial direction, pressing the central part of the diaphragm spring 21 in the direction of the arrow C. Therefore the diaphragm spring 21 deflects back on the wire rings 22, 23 as a fulcrum, thus removing a pressure that has been exerted to the clutch disc 19 to disconnect the clutch, and accordingly shutting off the transmission of power from the crankshaft 8 to the transmission drive shaft 18.
Subsequently, the operation of the starting and charging device of the above-mentioned constitution will be described. When the key switch not illustrated, is turned to the START position, with the engine left stationary, the current flows into the field coil 3 and the armature coil 5, thereby producing a torque at the field poles 2a, 2b to turn the crankshaft 8 directly coupled. When the field poles 2a, 2b have started turning, the crank angle detector 6 detects the positions of the field poles, and the armature current switching circuit switches the current to the armature coil 5 so that the speed of a rotating field formed by the armature coil 5 will be the same as the speed of rotation of the field poles; accordingly the field poles 2a, 2b will gain a torque for further acceleration. The device, thus producing the starting torque by virtue of such a positive feedback operation, starting the engine.
After the engine has started, the speed of rotation of the field poles further increases, thus increasing a back electromotive force produced at the armature coil 5; accordingly no unnecessary starting current will flow.
Furthermore, when, after the starting of the engine, the key switch is placed in the IGNITION position, the starting and charging device body 1 operates as an a.c. synchronous generator, which produces the electric current. The current thus produced is converted into the direct current by means of a converter which is not illustrated, and supplied to batteries and electrical equipment mounted on the motor vehicle.
The field pole 2a used in the prior-art engine starting and charging device, servicing also as an engine flywheel as stated above, must be much thicker than required to form a necessary magnetic path to support a centrifugal force to be applied to the rotating field poles 2a, 2b. Therefore it has such a problem that its weight will become excessive more than necessary.
Furthermore, the field poles 2a, 2b, constituting the magnetic path, are required to be produced of such a material of high permeability as S10C. Such a material, however, has low wear resistance and therefore is not suitable on account of low function as a clutch plate which comes in contact with the clutch disc 19.
Furthermore, there is a problem that the field pole 2a rises in temperature due to frictional heat caused by the connection and disconnection of the clutch 17, resulting in lowered operating characteristics.
Furthermore, the prior-art fixed field, made of the field core 11 of complicated configuration with the field coil 3 wound around as illustrated, has such a problem as low manufacturing and assembling efficiency, and accordingly it is hard to fix this field coil 3.